1. Field of the Invention
Embodiments of the invention relate to a liquid crystal display module (LCDM), and more particularly, to a backlight unit and an LCDM including the same.
2. Discussion of the Related Art
LCD devices include an LCD module. The LCD module includes an LCD panel that displays images and a backlight unit that supplies light to the LCD panel. The LCD panel includes two substrates facing each other and spaced apart from each other. A liquid crystal material is interposed therebetween. Liquid crystal molecules of the liquid crystal material have a dielectric constant and refractive index anisotropic characteristic due to their long thin shape. Two electric field generating electrodes are formed on the two substrates, respectively. An orientation alignment of the liquid crystal molecules may be controlled by supplying a voltage to the two electrodes to change the light transmittance of the LCD panel according to polarization properties of the liquid crystal material.
Generally, an additional light source is required because the LCD panel is a non-emissive-type display device. Accordingly, a backlight unit is disposed under the LCD panel. The LCD device displays images using light produced by the backlight unit and supplied to the LCD panel. Backlight units may be classified into a side-type backlight unit and a direct-type backlight unit in accordance with a disposition of the light source. The side-type backlight unit has one lamp or a pair of lamps disposed at a side portion of a light guide plate. Alternatively, at least one lamp is disposed at each side portion of the light guide plate, respectively.
The direct-type backlight unit has a plurality of lamps disposed under the light guide plate. In a large sized LCD module, the direct-type backlight unit may provide the LCD module with a uniform light source although the side-type backlight unit is more easily manufactured than the direct-type. Further, the direct-type backlight unit includes a plurality of fluorescent lamps disposed in a row. Thus, the direct-type backlight unit directly irradiates light toward the liquid crystal panel. Since the direct-type backlight unit has a high uniformity when light is irradiated, it is suitable to be applied to a large-size LCD. The light guide plate is unnecessary in the direct-type backlight unit because the direct-type backlight unit is directly irradiated on the entire surface of the liquid crystal panel. In particular, the direct-type backlight unit has advantages that light efficiency is high, the use is convenient, the display size is not substantially limited. For example, the direct-type backlight unit may be utilized in a large-size LCD such as a 20-inch model.
Generally, the liquid crystal panel and the backlight unit are combined with each other using a main frame, a top frame and a bottom frame to prevent light-loss and to protect them from outside impact.
FIG. 1 is a perspective view of an inverter unit connected to a backlight unit of an LCDM according to the related art. Referring to FIG. 1, a direct-type backlight unit includes a plurality of fluorescent lamps 24 disposed in a row on a bottom frame 50, and a reflective sheet 22 disposed under the plurality of fluorescent lamps 24 and on the bottom frame 50. A side support 33 for supporting the fluorescent lamps 24 is disposed at one end portion of the bottom frame 50. The end portion of each of the fluorescent lamps 24 is inserted into a lamp holder 32. In addition, the lamp holder 32 is inserted into an opening of the side support 33. Although not shown, an other side support (not shown) is disposed at the other end portions of the fluorescent lamps 24.
A plurality of wires 37, which are connected to an external circuit, extend from end portions of the plurality of fluorescent lamps 24 to a backside of the bottom frame 50, respectively. With respect to one of the wires 37, a socket connector 38a is formed at one end portion of the wire 37 to connect the wire 37 and the inverter unit 70. The inverter unit 70 is disposed under the bottom frame 50 and provides a power supply to the fluorescent lamps 24. The inverter unit 70 includes a plurality of inverters (not shown), a plug connector 38b connecting the wire 37 and the inverter unit 70, and an inverter PCB 35 on which the inverters and the plug connector 38b are mounted. A cover shield (not shown) protects the inverter unit 70 from an external impact. By combining the socket connector 38a and the plug connector 38b, a power source of the inverter unit 70 can be provided to the fluorescent lamp 24 through the wire 37. Because the wire 37 extends from the end portion of the fluorescent lamp 24 on a front side of the bottom frame 50 to a backside of the bottom frame 50, neither the bottom frame 50 nor cover shield (not shown) covers the wire 37 such that the current leakage can be generated from the wire 37. Moreover, the necessity of soldering each of the plurality of fluorescent lamps 24 independently to each of the wires 37 increases the manufacturing time.
The fluorescent lamp 24 emits light when an alternating current waveform of a high voltage is applied to an electrode of the fluorescent lamp 24 through the wire 37 connected to the electrode of the fluorescent lamp 24. In FIG. 1, a high-low type fluorescent lamp 24 including a ground portion at an end portion thereof is illustrated.
The high-low type fluorescent lamp 24 includes at least two fluorescent lamps 24 forming a pair of fluorescent lamps 24. The end portion of the fluorescent lamp 24 is inserted into a lamp holder 32, and the fluorescent lamp 24 is electrically connected to the inverter unit 70 through wire 37. The wire 37 extends to the backside of the bottom frame 50, and an end portion of the wire 37 is connected to the socket connector 38a. Here, the inverter unit 70, which changes a direct voltage into an alternating current of a high voltage, is required because the alternating current of the high voltage is demanded for driving the fluorescent lamp 24.
Accordingly, the inverter unit 70 and the inverter PCB 35 are independent from each other, and the inverter unit 70 is mounted on the inverter PCB 35. Since the inverter unit 70 dissipates a lot of heat, the inverter PCB 35 on which the inverter unit 70 is mounted is disposed on the backside of the bottom frame 50. The plug connector 38b is disposed on the inverter PCB 35 for being connected to the socket connector 38a. That is, the fluorescent lamp 24 is connected to the inverter PCB 35 by connecting the socket connector 38a to the plug connector 38b. 
The wires 37 are exposed along edges and the backside of the bottom frame 50 because the fluorescent lamps 24 and the inverter unit 70 are connected to each other using the wires 37 forming a bridge between the fluorescent lamps 24 and the inverter unit 70. Thus, even if the inverter unit 70 is bent toward the backside of the bottom frame 50, the wires 37 are still exposed along edges and the backside of the bottom frame 50. Further, defects due to an electric interference between the exposed wires 37 or current leakage may occur. Furthermore, a crack between the fluorescent lamp 24 and the wires 37 at the soldering portion may be occur. Accordingly, emission of the fluorescent lamps 24 cannot occur uniformly.
FIG. 2 is an exploded portion of region “IIa” in FIG. 1 according to the related art. In FIG. 2, a fluorescent lamp 24 is connected to a wire 37, and the socket connector 38a is connected to an end portion of the wire 37. Generally, the fluorescent lamp 24 and the wire 37 are manually soldered to each other, as shown in part “IIb” in FIG. 2. The process time and the process cost increase because of the manual soldering. Furthermore, the material cost of the wire 37 increases because individual wires 37 are used for each fluorescent lamp 24. Further, the socket connector 38a is connected to an end portion of the wire 37 for connecting the inverter unit 70 of FIG. 1.
FIG. 3 is a lamp holder portion of a backlight unit for the LCDM of FIG. 1 according to the related art. Referring to FIG. 3, the related art LCDM of FIG. 1 requires a lamp holder 32 to hold the fluorescent lamp 24 at the bottom frame 50 of FIG. 1.
The fluorescent lamp 24 may be one of a cold cathode fluorescent lamp (CCFL) having internal electrodes and an external electrode fluorescent lamp (EEFL) having external electrodes. When the direct-type backlight unit including CCFL is driven by a parallel driving method using one inverter, there is problem that only part of the fluorescent lamps are driven properly due to differences in the charge characteristics of CCFLs. Although CCFLs have the same unlimited resistant value before charging, CCFLs can have different small resistant values when charged due to different conductor state plasmas that are generated inside of the glass tubes of each of the CCFLs. Accordingly, the resistant values of CCFLs after charging can be substantially different. Therefore, when a plurality of CCFLs are driven by a parallel driving method, more current flows in the fluorescent lamps having smaller resistant value after a primary charge. Accordingly, there is a problem in that some of the CCFLs will not be driven properly. Consequently, the direct-type backlight unit including CCFLs should include a number of inverters corresponding to the number of fluorescent lamps so that there is a one-to-one driving of the CCFLs.